1. Field of the Invention
The invention concerns a process for the continuous production of steel with the use of metal charge materials, such as scrap, sponge iron, or the like, wherein the charge materials are preheated in an upper part of a melting vessel and then melted in a lower part of the melting vessel using fossil fuels, wherein the molten metal is continuously discharged into a treatment vessel, in which the desired grade of steel is adjusted, and wherein gases are introduced into the melting vessel from the outside for post combustion of the process gases.
2. Description of the Related Art
The invention also concerns equipment for the continuous production of steel with the use of metal charge materials, which comprises a melting vessel with at least one fossil fuel burner that acts on the metal charge materials in a lower part of the melting vessel, and a treatment vessel, which is connected with the lower part of the melting vessel by a taphole, such that the molten metal is continuously discharged into the treatment vessel, in which the desired grade of steel is adjusted, such that the charge materials are preheated in an upper part of the melting vessel by the process gases, and such that gases are introduced into the melting vessel from the outside for post combustion of the process gases. In the treatment vessel, the molten iron is subjected especially to superheating and an alloying treatment to produce steel.
A method of this type and equipment of this type are described in DT 2 325 593. A method is described for the continuous production of steel with the use of charge materials, such as scrap, sponge iron, or the like, which are continuously melted from below by a burner lance in a shaft furnace, which serves as the melting vessel, wherein the molten metal is discharged into a heated continuous vessel, in which slag separation is carried out continuously, and wherein the material present in the vessel is superheated, and the desired steel analysis is adjusted by the addition of suitable alloying additives and deoxidation additives. The superheating and slag reduction are accomplished electrically. The continuous vessel is heated for this purpose by induction or by an electric arc. A lance-like oil/oxygen burner is inserted in the shaft furnace by means of a lance guide in such a way that it can be moved vertically into the interior of the melting vessel, and the flame produced by the burner acts on the charge material from below and continuously melts it. Air for post-combustion of the exhaust gases from the melting process, which are used to preheat the material to be melted, can be introduced through an annular gap in the casing of the shaft furnace. The interior of the melting vessel is essentially cylindrical and can have a diameter that increases slightly towards the bottom.
This continuous process of melting scrap by the countercurrent principle is also described in Stahl und Eisen, 92 (1972), No. 11, p. 501. In this mode of operation, a column of scrap is melted from below with an oil/oxygen burner. The molten metal runs continuously out of the melting vessel together with the iron oxide slag that forms. At the same time, the column of scrap is replenished by continuous recharging. A problem associated with this process is that, although the sensible heat is used, the share of chemically bound exhaust gas heat remains unutilized for preheating. Moreover, the process has the problem of high iron oxidation due to the use of fossil fuels in combination with oxygen.
A different direction of development is described in Stahl und Eisen 115 (1995), No. 5, p. 75. In this case, scrap is preheated in a preheating column and melted down in an iron bath reactor. Either the preheating can occur in the iron bath reactor itself before the melting, or the scrap is preheated in a basket located above the melting reactor and then allowed to fall into the reactor. During the melting, coal and oxygen are blown into the iron bath, and the exhaust gases can be post-combusted above the melt in the reactor. To minimize oxidation of the scrap during the preheating, the fuel gas is burned in stages during the preheating.